The method prime? is 20x slower then MRI.
But a method implemented by myself give the same time as MRI prime? in MRI and jruby.
I think the problem is in the library prime.
Try

require 'prime'
require 'benchmark'
n = 1090109110921093
Benchmark.bm do |r|
  4.times do
    r.report {puts n.prime?}
  end
end

Tiziano Merzi

P.S.
jruby 9.0.5.0 on MAC